I need some help w/ a driveline vibration. I recently lowered my 95 F150 Lightning w/ 3" frt & a 4" rr drop & I'm experiencing it above 40mph. I tried adjusting the pinion angle from 5.5* down to now 5.5* up & it still vibrates. The tailshaft is @ 5.5* down, u-joints are good & tires have been recently balanced. Any ideas?